determining rdns capability

[Greg Hudson]

On 11/15/2012 11:46 AM, Ken Dreyer wrote:
> For msktutil, I recently received a patch to optionally set "rdns =
> false".
[...]
> What is the best way to determine MIT's rdns capability?

I don't believe there is one, because that knob was never envisioned as
being application-controllable.  I'm kind of curious how such a patch
could even work, and I'd question whether it's a good idea for some
applications to turn off rdns while others don't.

Whether "rdns = false" will work is complicated by the odd, probably
buggy behavior of getaddrinfo in some (maybe all) versions of glibc.
glibc does a PTR lookup for AI_CANONNAME if AI_ADDRCONFIG or
hints.ai_family is also used.  We worked around this behavior in 1.10.2
by changing how we call getaddrinfo().